In the event of short circuits, the thermal and electrodynamic load on electrical systems should be kept as low as possible. In particular, the magnitude of the short-circuit current should be limited.
When a short circuit is disconnected by a circuit breaker, this is achieved by an arc voltage very rapidly opposing the driving voltage. This is achieved by rapid opening of the contact point in the circuit breaker, so that the arc is guided quickly and is driven into the quenching plates, where it is split into a number of arc elements. This arc voltage counteracts the driving voltage and thus limits the short-circuit current. The level of limiting depends on the time which is required to produce the arc voltage. This is in turn dependent on the contact opening time.